This update fixes a problem in which a calendar item that is marked as private is opened if it is found by using the Search Desktop feature. The update also fixes performance issues that occur when you work with items in a large .pst file or .ost file.

http://www.microsoft.com/downloads/details.aspx?FamilyID=c262bcfd-1e09-49b6-9003-c4c47539df66&DisplayLang=en